This 4.3x standard zoom lens is the latest addition to Sigma's new 'Art' line of lenses that promise excellent optical quality. It can be picked up for around £700 and as it is one of Sigma's top of the range lenses, it sports a hypersonic focusing motor, optical stabilisation, brass lens mount and build quality previously reserved for their EX line of lenses. It is available to fit, Sigma, Canon, Nikon and Sony SLR cameras. In this review, we'll take a close look at how it performs.

Sigma 24-105mm f/4 DG OS HSM A Handling and Features

Weighing around 885g, this certainly isn't a lightweight lens. High quality plastics and metals with a glossy finish have been used for much of the lens barrel, which provides a good tactile feel to the lens and a metal lens mount adds to the overall robust feel of the lens. However, Sigma make no claims about this lens being resistant to dust and moisture. The lens balances well on the Canon EOS 5D Mark III used for testing, but as this lens is quite large for a standard zoom at 109mm long and reasonably weighty, combining it with some of the more compact DSLRs available may result in an unbalanced pairing.

A silent HSM focusing motor powers autofocus, resulting in quick focus acquisition and the ability to apply manual focus adjustments at any time. The manual focus ring is well damped, but is quite narrow, which can hamper operation a little. Focusing is performed internally, so the huge 82mm filter thread does not rotate, making this lens ideal for use with polarising and graduated filters, if you can afford them in that size. The close focusing distance of 45cm is fairly typical of this kind of lens.

The optical stabilisation system fitted to this lens promises to allow sharp images to be taken at shutter speeds slower than would be possible without the system enabled. Sharp images can be produced around half the time with shutter speeds as low as 1/13sec at 105mm, which is roughly three stops slower than the usual rule of thumb would dictate necessary.

Sigma 24-105mm f/4 DG OS HSM A Performance

At 24mm, sharpness is already outstanding in the centre of the frame at maximum aperture and approaching excellent levels of clarity towards the edges. In fact, diffraction appears to be the limiting factor on performance at this focal length, with sharpness towards the edges of the frame increasing slightly at f/5.6, otherwise there is no performance gain from stopping down.

This high level of performance is maintained at 50mm, with outstanding sharpness in the centre and excellent clarity towards the edges of the frame at maximum aperture. Stopping down to between f/5.6 and f/8 results in peak performance as sharpness is outstanding across the frame.

Finally, at 105mm, there is a slight drop in performance at maximum aperture, with sharpness in the centre approaching excellent levels in the centre of the frame, and good clarity being produced towards the edges of the frame. Peak performance for this focal length is realised at f/8, where sharpness improves to outstanding levels across the frame.

MTF@24mm

MTF@50mm

MTF@105mm

How to read our charts

The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column.

The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple.

Chromatic aberrations are reasonably well controlled, just exceeding 0.75 pixel widths at 105mm and f/4, as well as f/22 at 24mm. This low level of CA should pose few issues, even in large prints, or harsh crops from the edges of the frame.

CA@24mm

CA@50mm

CA@105mm

How to read our charts

Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.

Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more.

Falloff of illumination towards the corners of the frame is fairly well controlled. At 24mm the corners are 1.9 stops darker than the image centre and at 105mm the corners are 1.7 stops darker than the centre. Visually uniform illumination isn't achieved until the lens is stopped down to f/8 or beyond throughout the zoom range.

Barrel distortion can be quite noticeable at 24mm, with 4.5% barrelling being present. This is replaced with 1.31% pincushion distortion at 105mm, which is a very mild amount of distortion. If straight lines are paramount, then you'll be glad to hear that the distortion pattern is uniform across the frame at both ends of the zoom range, which should make applying corrections in image editing software fairly straightforward.

A petal-shaped hood is supplied as standard with the lens, which does a decent job of shading the lens from extraneous light that may cause unwanted flare and loss of contrast. During testing there were no issues with flare and contrast holds up well, even when shooting into the light.

Sigma 24-105mm f/4 DG OS HSM A Sample Photos

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Value For Money

The price of around £700 and specification of this lens is comparable to those of lenses produced by the main camera manufacturers.

The closest equivalent for Canon cameras is their popular 24-105mm f/4L IS USM lens, which sports virtually identical specifications, but is currently around £100 less expensive.

Nikon camera owners looking at their 24-120mm f/4 VR lens may also consider this offering from Sigma. Although the Nikon lens offers slightly more telephoto reach, it is around £100 dearer than this Sigma optic.

Sony don't offer a standard zoom lens with a constant f/4 maximum aperture, or covering this focal length range currently, so this lens may be of particular interest to those who own a Sony Alpha SLR, or SLT camera.

Sigma 24-105mm f/4 DG OS HSM A Verdict

With their latest lens releases, Sigma appear to be changing their past image of a manufacturer of lenses that are less expensive than the major camera manufacturers, instead concentrating on lenses that deliver performance to rival the best available.

This lens certainly is capable of producing outstanding clarity, at a price that is comparable to those of camera manufacturers own lenses. It should certainly be considered as a viable alternative if you're in the market for a lens of this specification.